By way of example, a pump of this type is described in the prior art, in document FR 2 343 137. The sleeve that slides over the actuator rod is made integrally with the piston that slides in leaktight manner inside the pump body. In the rest position, the part forming the sleeve and the piston is urged by a return spring against a valve gasket. The actuator rod is urged into its rest position by a pre-compression spring that bears against the part forming the sleeve and the piston. The sleeve that slides over the actuator rod includes a piece of trim that, in the rest position, obstructs a side orifice in leaktight manner. The side orifice is merely in the form of a cylindrical hole of circular shape. Its diameter is about one tenth of a millimeter. With regard to the maximum stroke of the sleeve over the actuator rod, it is about one millimeter. Thus, the side orifice may be considered as an outlet that is localized compared to the maximum stroke of the sleeve over the actuator rod.
When the user presses on the pusher mounted on the free end of the actuator rod, said actuator rod is driven into the pump body and reduces the volume of the pump chamber. In response, the part forming the sleeve and the piston is urged, both by the pre-compression spring and by the increased pressure that exists in the pump chamber, in the direction opposite to the direction of the actuator rod, thereby causing the trim of the sleeve to uncover the side orifice of the actuator rod. Thus, the fluid put under pressure in the pump chamber finds an outlet passage through the side orifice from where it then flows into an internal channel inside the actuator rod as far as the pusher. This design is entirely conventional for a manual pre-compression pump in the fields of perfumery, cosmetics, and even pharmacy.
With such a pump, the quality and the form of the spray at the outlet from the nozzle of the pusher are constant, whatever the force exerted by the user on the pusher. The spray from the nozzle of the pusher is directly dependent on the stiffness of the return and pre-compression springs, and above all on the flow sections for the fluid from the pump chamber to the outlet from the nozzle. Thus, the single side-orifice of the actuator rod that acts as an outlet passage from the pump chamber, creates considerable head loss that is largely responsible for determining the quality and the nature of the spray. In other words, it can be said that it is the side orifice of the actuator rod alone that determines the form and the quality of the spray, assuming that the stiffnesses of the springs and the type of nozzle are constant parameters. As a result, regardless of whether the user presses gently or vigorously on the pusher, the fluid that passes through the side orifice of the actuator rod always presents physical characteristics that are constant in terms of quantity, flowrate, and pressure.
An object of the present invention is to vary the quality and the nature of the spray as a function of the intensity of the force exerted on the pusher. More precisely, the present invention seeks to create a spray that is light and long-lasting when the user presses gently on the pusher, and a spray that is powerful and short-lived when the user presses energetically on the pusher. Thus, the invention seeks to reproduce the dynamics with which the pusher is actuated in terms of the power, the configuration, and the duration of the spray. A direct correlation thus exists between the behavior of the user while actuating the pump, and the nature of the spray.